//===-- llvm/Support/Casting.h - Allow flexible, checked, casts -*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the isa<X>(), cast<X>(), dyn_cast<X>(), cast_or_null<X>(),
// and dyn_cast_or_null<X>() templates.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_CASTING_H
#define LLVM_SUPPORT_CASTING_H

#include "Compiler.h"
#include "type_traits.h"
#include <cassert>

namespace llvm {

//===----------------------------------------------------------------------===//
//                          isa<x> Support Templates
//===----------------------------------------------------------------------===//

// Define a template that can be specialized by smart pointers to reflect the
// fact that they are automatically dereferenced, and are not involved with the
// template selection process...  the default implementation is a noop.
//
template<typename From> struct simplify_type {
    typedef From SimpleType; // The real type this represents...

    // An accessor to get the real value...
    static SimpleType &getSimplifiedValue(From &Val) { return Val; }
};

template<typename From> struct simplify_type<const From> {
    typedef typename simplify_type<From>::SimpleType NonConstSimpleType;
    typedef typename add_const_past_pointer<NonConstSimpleType>::type SimpleType;
    typedef typename add_lvalue_reference_if_not_pointer<SimpleType>::type RetType;
    static RetType getSimplifiedValue(const From &Val) { return simplify_type<From>::getSimplifiedValue(const_cast<From &>(Val)); }
};

// The core of the implementation of isa<X> is here; To and From should be
// the names of classes.  This template can be specialized to customize the
// implementation of isa<> without rewriting it from scratch.
template<typename To, typename From, typename Enabler = void> struct isa_impl {
    static inline bool doit(const From &Val) { return To::classof(&Val); }
};

/// \brief Always allow upcasts, and perform no dynamic check for them.
template<typename To, typename From> struct isa_impl<To, From, typename std::enable_if<std::is_base_of<To, From>::value>::type> {
    static inline bool doit(const From &) { return true; }
};

template<typename To, typename From> struct isa_impl_cl {
    static inline bool doit(const From &Val) { return isa_impl<To, From>::doit(Val); }
};

template<typename To, typename From> struct isa_impl_cl<To, const From> {
    static inline bool doit(const From &Val) { return isa_impl<To, From>::doit(Val); }
};

template<typename To, typename From> struct isa_impl_cl<To, From *> {
    static inline bool doit(const From *Val) {
        assert(Val && "isa<> used on a null pointer");
        return isa_impl<To, From>::doit(*Val);
    }
};

template<typename To, typename From> struct isa_impl_cl<To, From *const> {
    static inline bool doit(const From *Val) {
        assert(Val && "isa<> used on a null pointer");
        return isa_impl<To, From>::doit(*Val);
    }
};

template<typename To, typename From> struct isa_impl_cl<To, const From *> {
    static inline bool doit(const From *Val) {
        assert(Val && "isa<> used on a null pointer");
        return isa_impl<To, From>::doit(*Val);
    }
};

template<typename To, typename From> struct isa_impl_cl<To, const From *const> {
    static inline bool doit(const From *Val) {
        assert(Val && "isa<> used on a null pointer");
        return isa_impl<To, From>::doit(*Val);
    }
};

template<typename To, typename From, typename SimpleFrom> struct isa_impl_wrap {
    // When From != SimplifiedType, we can simplify the type some more by using
    // the simplify_type template.
    static bool doit(const From &Val) {
        return isa_impl_wrap<To, SimpleFrom, typename simplify_type<SimpleFrom>::SimpleType>::doit(
        simplify_type<const From>::getSimplifiedValue(Val));
    }
};

template<typename To, typename FromTy> struct isa_impl_wrap<To, FromTy, FromTy> {
    // When From == SimpleType, we are as simple as we are going to get.
    static bool doit(const FromTy &Val) { return isa_impl_cl<To, FromTy>::doit(Val); }
};

// isa<X> - Return true if the parameter to the template is an instance of the
// template type argument.  Used like this:
//
//  if (isa<Type>(myVal)) { ... }
//
template<class X, class Y> LLVM_ATTRIBUTE_UNUSED_RESULT inline bool isa(const Y &Val) {
    return isa_impl_wrap<X, const Y, typename simplify_type<const Y>::SimpleType>::doit(Val);
}

//===----------------------------------------------------------------------===//
//                          cast<x> Support Templates
//===----------------------------------------------------------------------===//

template<class To, class From> struct cast_retty;

// Calculate what type the 'cast' function should return, based on a requested
// type of To and a source type of From.
template<class To, class From> struct cast_retty_impl {
    typedef To &ret_type; // Normal case, return Ty&
};
template<class To, class From> struct cast_retty_impl<To, const From> {
    typedef const To &ret_type; // Normal case, return Ty&
};

template<class To, class From> struct cast_retty_impl<To, From *> {
    typedef To *ret_type; // Pointer arg case, return Ty*
};

template<class To, class From> struct cast_retty_impl<To, const From *> {
    typedef const To *ret_type; // Constant pointer arg case, return const Ty*
};

template<class To, class From> struct cast_retty_impl<To, const From *const> {
    typedef const To *ret_type; // Constant pointer arg case, return const Ty*
};

template<class To, class From, class SimpleFrom> struct cast_retty_wrap {
    // When the simplified type and the from type are not the same, use the type
    // simplifier to reduce the type, then reuse cast_retty_impl to get the
    // resultant type.
    typedef typename cast_retty<To, SimpleFrom>::ret_type ret_type;
};

template<class To, class FromTy> struct cast_retty_wrap<To, FromTy, FromTy> {
    // When the simplified type is equal to the from type, use it directly.
    typedef typename cast_retty_impl<To, FromTy>::ret_type ret_type;
};

template<class To, class From> struct cast_retty {
    typedef typename cast_retty_wrap<To, From, typename simplify_type<From>::SimpleType>::ret_type ret_type;
};

// Ensure the non-simple values are converted using the simplify_type template
// that may be specialized by smart pointers...
//
template<class To, class From, class SimpleFrom> struct cast_convert_val {
    // This is not a simple type, use the template to simplify it...
    static typename cast_retty<To, From>::ret_type doit(From &Val) {
        return cast_convert_val<To, SimpleFrom, typename simplify_type<SimpleFrom>::SimpleType>::doit(simplify_type<From>::getSimplifiedValue(Val));
    }
};

template<class To, class FromTy> struct cast_convert_val<To, FromTy, FromTy> {
    // This _is_ a simple type, just cast it.
    static typename cast_retty<To, FromTy>::ret_type doit(const FromTy &Val) {
        typename cast_retty<To, FromTy>::ret_type Res2 = (typename cast_retty<To, FromTy>::ret_type) const_cast<FromTy &>(Val);
        return Res2;
    }
};

template<class X> struct is_simple_type { static const bool value = std::is_same<X, typename simplify_type<X>::SimpleType>::value; };

// cast<X> - Return the argument parameter cast to the specified type.  This
// casting operator asserts that the type is correct, so it does not return null
// on failure.  It does not allow a null argument (use cast_or_null for that).
// It is typically used like this:
//
//  cast<Instruction>(myVal)->getParent()
//
template<class X, class Y>
inline typename std::enable_if<!is_simple_type<Y>::value, typename cast_retty<X, const Y>::ret_type>::type cast(const Y &Val) {
    assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
    return cast_convert_val<X, const Y, typename simplify_type<const Y>::SimpleType>::doit(Val);
}

template<class X, class Y> inline typename cast_retty<X, Y>::ret_type cast(Y &Val) {
    assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
    return cast_convert_val<X, Y, typename simplify_type<Y>::SimpleType>::doit(Val);
}

template<class X, class Y> inline typename cast_retty<X, Y *>::ret_type cast(Y *Val) {
    assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
    return cast_convert_val<X, Y *, typename simplify_type<Y *>::SimpleType>::doit(Val);
}

// cast_or_null<X> - Functionally identical to cast, except that a null value is
// accepted.
//
template<class X, class Y> LLVM_ATTRIBUTE_UNUSED_RESULT inline
typename std::enable_if<!is_simple_type<Y>::value, typename cast_retty<X, const Y>::ret_type>::type
cast_or_null(const Y &Val) {
    if (!Val)
        return nullptr;
    assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
    return cast<X>(Val);
}

template<class X, class Y> LLVM_ATTRIBUTE_UNUSED_RESULT inline
typename std::enable_if<!is_simple_type<Y>::value, typename cast_retty<X, Y>::ret_type>::type
cast_or_null(Y &Val) {
    if (!Val)
        return nullptr;
    assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
    return cast<X>(Val);
}

template<class X, class Y> LLVM_ATTRIBUTE_UNUSED_RESULT inline typename cast_retty<X, Y *>::ret_type cast_or_null(Y *Val) {
    if (!Val)
        return nullptr;
    assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
    return cast<X>(Val);
}

// dyn_cast<X> - Return the argument parameter cast to the specified type.  This
// casting operator returns null if the argument is of the wrong type, so it can
// be used to test for a type as well as cast if successful.  This should be
// used in the context of an if statement like this:
//
//  if (const Instruction *I = dyn_cast<Instruction>(myVal)) { ... }
//

template<class X, class Y> LLVM_ATTRIBUTE_UNUSED_RESULT inline
typename std::enable_if<!is_simple_type<Y>::value, typename cast_retty<X, const Y>::ret_type>::type
dyn_cast(const Y &Val) {
    return isa<X>(Val) ? cast<X>(Val) : nullptr;
}

template<class X, class Y> LLVM_ATTRIBUTE_UNUSED_RESULT inline typename cast_retty<X, Y>::ret_type dyn_cast(Y &Val) {
    return isa<X>(Val) ? cast<X>(Val) : nullptr;
}

template<class X, class Y> LLVM_ATTRIBUTE_UNUSED_RESULT inline typename cast_retty<X, Y *>::ret_type dyn_cast(Y *Val) {
    return isa<X>(Val) ? cast<X>(Val) : nullptr;
}

// dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
// value is accepted.
//
template<class X, class Y> LLVM_ATTRIBUTE_UNUSED_RESULT inline
typename std::enable_if<!is_simple_type<Y>::value, typename cast_retty<X, const Y>::ret_type>::type
dyn_cast_or_null(const Y &Val) {
    return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
}

template<class X, class Y> LLVM_ATTRIBUTE_UNUSED_RESULT inline
typename std::enable_if<!is_simple_type<Y>::value, typename cast_retty<X, Y>::ret_type>::type
dyn_cast_or_null(Y &Val) {
    return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
}

template<class X, class Y> LLVM_ATTRIBUTE_UNUSED_RESULT inline typename cast_retty<X, Y *>::ret_type dyn_cast_or_null(Y *Val) {
    return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
}

} // namespace llvm

#endif
